Part A
What is the wavelength of light in glass, if its wavelength in air is
, and its speed in the glass is .
Express your answer in terms of
, its speed in air is
, , and .
=(lambda_0/c)*vCorrect
The letter is used to denote the speed of light in a vacuum. Although the speed of light
in air should have been used for this part, the speeds of light in air and vacuum are so
similar that they are often used interchangeably. You should always keep this in mind, as
problems that ask for many significant figures will require you to use the correct speed in
air. For the rest of this problem, however, assume that the difference between the speeds
of light in air and vacuum is too small to affect your results.
Part B
The index of refraction for a material is defined as
Part A in terms of index of refraction.
Express your answer in terms of
. Rewrite your answer from
and .
=lambda_0/nCorrect
Part C
If red light of wavelength
in air enters glass with index 1.5, what is the
wavelength in the glass ?
Express your answer in nanometers to three significant figures.
=467.0
Correct
Two important things happen to light when it strikes a transparent boundary: It gets
reflected and it gets refracted. When you see your reflection in a pond or river, you are
seeing the results of reflection from a transparent boundary. In the figure
, the ray
moving toward the air/glass interface is called the incident ray. The ray leaving the
boundary in air is called the reflected ray. The ray leaving the boundary inside the glass is
called the refracted ray.
Reflection from a mirror and reflection from transparent boundaries both obey the law of
reflection. The law of reflection is stated as
, where
is the angle between the
incoming ray and the normal line (i.e., a line perpendicular to the surface) and
angle between the normal line and the reflected ray
.
is the
Part D
If light strikes the air/glass interface at an angle
to the normal, what is
between the normal and the reflected ray?
Express your answer in degrees to three significant figures.
, the angle
=32.00 Correct
The second important effect of light striking a transparent boundary is refraction.
Refraction is the bending of light caused by the difference in the speed of light between
materials. To understand this effect, it may be helpful to picture wavefronts approaching
the boundary at an angle. The parts of the wavefronts that enter the glass first slow down.
This difference in speed causes the wavefronts to bend downward, toward the normal
line. Any time that light moves into a medium with a higher index of refraction (i.e.,
lower speed of light), the refracted ray has a smaller angle to the normal than the incident
ray. Refraction follows a law known as Snell's law, which has the form
. Since we are assuming that the speed of light in air is very
close to the speed of light in vacuum, you will use
in this problem. Note that the
"angle between the incident ray and the normal" is usually shortened to just the "angle of
incidence," and similarly the "angle between the refracted ray and the normal" is
shortened to "angle of refraction."
Part E
If light strikes the air/glass interface at an angle of
with respect to the normal of the
surface, what is the angle of refraction ? Use 1.50 for the index of refraction of glass.
Express your answer in degrees to three significant figures.
=20.70 Correct
Part F
Now, use your answers from Parts D and E to find the angle between the reflected ray
and the refracted ray, if the angle of incidence is
.
Express your answer in degrees to three significant figures.
Angle between reflected and refracted rays =127.0 Correct